This invention relates to a method for the separation of hydrogen isotopes. More particularly, this invention relates to a method for deuterium enrichment by an infrared single-photon induced addition reaction.
Several processes for isotope separation make use of the isotope shift, that is, a slight shift of the lines in the absorption spectra of elements or molecular species due to the small difference in nuclear mass of the isotopes of the same element contained therein. Changes in nuclear mass can cause a shift in electronic, vibrational, and rotational energy levels. When the shift places the absorption line of one isotopic species at a frequency at which the others are transparent, it is possible to excite selectively that species with a source of radiation of sufficiently narrow width.
A common feature of all separation methods based on the isotope shift is the selective excitation of one of the isotopic species by radiation, particularly laser radiation, tuned to a specific absorption line, followed by a physical or chemical process which acts on excited species and separates them from unexcited ones. The physical or chemical separation process may or may not require the absorption of an additional photon.
Photochemical isotope separation processes involve radiation of a chemical system with monochromatic radiation under a set of circumstances which will cause chemical change or reaction preferentially to one isotopic variety of a molecular species. Mercury, carbon, oxygen, and chlorine have been enriched photochemically. C. B. Moore, Accounts of Chemical Research 6 323 (1973) describes the separation of hydrogen, carbon, and oxygen isotopes by the photopredissociation of formaldehyde.
Recent work has verified the usefulness of formaldehyde photodissociation as a simple and effective route to separation of deuterium, carbon and oxygen isotopes (J. B. Marling, "Laser Isotope Separation of Deuterium", Chem. Phys. Lett. 34, 84, 1974, and J. B. Marling, "Laser Enrichment of Oxygen-18 and Carbon-13 by Formaldehyde Photo-predissociation", UCRL-77521, December 1975). However, in the case of deuterium this process requires highly monochromatic nearultraviolet photons and economic considerations force laser efficiency to exceed 1%. This is an order of magnitude higher than what can be confidently achieved with present technology. Deuterium production by UV lasers would require an average optical power of at least 1 kilowatt per ton/year D.sub.2 O production, or a fractional megawatt of UV for a typical industrial sized plant. This cannot be easily envisioned from the presently available laser technology. The need exists for a highly selective photochemical process for the separation of deuterium which utilizes established high performance infrared lasers.